A steer axle assembly for a heavy-duty vehicle includes a knuckle at each end of a laterally extending axle beam or housing. A king pin is used to couple each knuckle to the axle housing. A steering arm is mounted to one of the knuckles and receives steering input from a steering wheel. As the vehicle is steered, steering input from the steering arm rotates the associated spindle and wheel about the king pin.
Traditionally, the king pin is fixed to the knuckle and is rotatably mounted on the axle housing. In this mounting configuration, the king pin was able to rotate relative to the axle housing but the knuckle was not able to rotate relative to the king pin. Also, in a typical mounting configuration, suspension components such as shock absorbers, struts, and associated brackets, etc., are mounted on the axle housing to accommodate road load inputs. These suspension components are mounted to, or supported by, the axle housing via bearings and fasteners.
This traditional mounting configuration requires the shock absorber to be large enough to accommodate significant road load inputs for heavy duty applications. Thus, traditional shock absorbers for heavy-duty vehicles tend to be bulky and are difficult to package within a very limited amount of available space. Another disadvantage with this traditional mounting configuration is that, due to the inboard location of the shock absorber, the amount of wheel travel is limited. Further, this mounting configuration has a large moment arm on the axle housing, which undesirably increases the size of the axle housing.
Thus, there is a need for a suspension configuration that does not require the shock absorber to be mounted to the axle housing to provide greater wheel travel, and to allow for a more compact axle housing configuration.